package com.it.tydic.estate.common.util;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;


public class IdWorker {
	private final static Logger logger = LoggerFactory.getLogger(IdWorker.class);
	  private long workerId;
	    private long datacenterId;
	    private long sequence = 0L;
	 
	    private long workerIdBits = 5L;
	    private long datacenterIdBits = 5L;
	    private long maxWorkerId = -1L ^ (-1L << workerIdBits);
	    private long maxDatacenterId = -1L ^ (-1L << datacenterIdBits);
	    private long sequenceBits = 12L;
	 
	    private long workerIdShift = sequenceBits;
	    private long datacenterIdShift = sequenceBits + workerIdBits;
	    private long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;
	    private long sequenceMask = -1L ^ (-1L << sequenceBits);
	 
	    private long lastTimestamp = -1L;
	 
	    public IdWorker(long workerId, long datacenterId) {
	        // sanity check for workerId
	        if (workerId > maxWorkerId || workerId < 0) {
	            throw new IllegalArgumentException(String.format("worker Id can't be greater than %d or less than 0", maxWorkerId));
	        }
	        if (datacenterId > maxDatacenterId || datacenterId < 0) {
	            throw new IllegalArgumentException(String.format("datacenter Id can't be greater than %d or less than 0", maxDatacenterId));
	        }
	        this.workerId = workerId;
	        this.datacenterId = datacenterId;
	        logger.info(String.format("worker starting. timestamp left shift %d, datacenter id bits %d, worker id bits %d, sequence bits %d, workerid %d", timestampLeftShift, datacenterIdBits, workerIdBits, sequenceBits, workerId));
	    }
	 
	    public synchronized long nextId() {
	        long timestamp = TimeUtil.timeGen();
	 
	        if (timestamp < lastTimestamp) {
	        	logger.error(String.format("clock is moving backwards.  Rejecting requests until %d.", lastTimestamp));
	            throw new RuntimeException(String.format("Clock moved backwards.  Refusing to generate id for %d milliseconds", lastTimestamp - timestamp));
	        }
	 
	        if (lastTimestamp == timestamp) {
	            sequence = (sequence + 1) & sequenceMask;
	            if (sequence == 0) {
	                timestamp = TimeUtil.tilNextMillis(lastTimestamp);
	            }
	        } else {
	            sequence = 0L;
	        }
	 
	        lastTimestamp = timestamp;
	 
	        return (timestamp << timestampLeftShift) | (datacenterId << datacenterIdShift) | (workerId << workerIdShift) | sequence;
	    }
}
